textproduct: Albany

WHAT HAS CHANGED

The zone of steadier snow for Wednesday afternoon into Wednesday night has shifted southward and now includes more of the Interstate 90 corridor. Winter Weather Advisories have been issued for much of eastern New York and western New England for Wednesday afternoon into Wednesday night for accumulating snow and/or freezing rain.

KEY MESSAGES

1) Low pressure system will bring rain, snow and a wintry mix, including freezing rain, to eastern New York and western New England Wednesday into Wednesday night resulting in slippery travel conditions, including for the Wednesday evening commute.

2) Another period of rain, snow and a wintry mix, including freezing rain, will lead to slippery travel conditions Friday into Friday night.

3) Potential coastal storm for late Sunday into Monday may produce impacts for the early week commute with snow or a wintry mix.

DISCUSSION

KEY MESSAGE 1...

A cold front, crossing the region into tonight, will stall just to the south of the area by Wednesday morning. An area of low pressure will track along the front Wednesday afternoon into Wednesday night. Upper level forcing from an approaching shortwave and convergent flow along the stalled front will support an area of precipitation overspreading the area late Wednesday morning into the afternoon and continuing into Wednesday night. There had been some uncertainty in the placement of the front and precipitation types in recent days, but better consensus today has placed the area of steadier snow along and just north of the Interstate 90 corridor. Precipitation in these areas may start out as rain or a rain/snow mix or even localized pockets of freezing rain, but will gradually transition to all snow following wet bulb and dynamic cooling processes. There is a window for a period of heavy snow to occur with mid-level FGEN focused right along the I-90 corridor and the potential for the greatest lift (omega) to intersect the dendritic growth zone (DGZ) for a time, which could lead to snowfall rates reaching 0.5 inches and 1 inch per hour. With the zone of steadiest snow rather narrow, some slight fluctuations in its placement and amounts are still possible but at least expect a period of accumulating snow to fall in these areas leading to slippery travel conditions. Snowfall accumulations in this snow area look to range from 2 to 6 inches.

South of Interstate 90, a mix of freezing rain or plain rain is expected to start, pending surface temperatures, with a gradual transition to snow and/or a wintry mix Wednesday night as colder air slowly advances southward. Lesser snow amounts are expected in these areas (generally up to 2 inches) but coverage of freezing rain looks to be greater than farther north (up to one tenth of an inch, especially in the higher elevations). Most of the mid- Hudson Valley region into Litchfield County looks to be mostly rain but may briefly end as freezing rain if the cold air arrives before precipitation tapers off Wednesday night.

With the increasing confidence in snow and ice accumulations, Winter Weather Advisories have been posted for much of eastern New York and western New England with the exception of northern Warren and northern Washington Counties (for less than 3 inches of snow forecast) and Litchfield, Dutchess and eastern Ulster Counties (for little or no snowfall and uncertainty whether or not freezing rain occurs). It is important to note that temperatures will fall back into the teens and 20s areawide Wednesday night, which could lead to any remaining wet and untreated surfaces to become icy, even in areas not in an advisory.

KEY MESSAGE 2...

A brief break in the wintry precipitation is expected on Thursday as the system from Wednesday departs and high pressure builds southward from Canada. Some breaks of sun are expected for most areas which will allow for temperatures to rebound above freezing for most areas by Thursday afternoon. As the high slides off to the east Thursday night, another low pressure system tracking northeastward across the Upper Great Lakes will send a warm/occluded front across the area for Friday. Isentropic lift along this front will bring another round of mixed precipitation. With this event, precipitation may start out as mostly snow but transition to a wintry mix and/or rain Friday afternoon into Friday night with the changeover to rain favored for valley areas as temperatures slowly rise through the day. Periods of rain and snow will likely linger into the start of Saturday as well before the system departs to the east. Additional light snow (1 to 4 inches possible) and ice amounts (up to around one tenth of an inch) may eventually warrant another round of Winter Weather Advisories for parts of the area.

KEY MESSAGE 3...

The ensembles, extended AI, NBM and medium range deterministic guidance continues to show a potential winter storm developing near the East Coast late in the weekend, and potentially tracking close enough for impacts late Sunday into Monday across eastern NY and western New England. We maintained and slightly increase PoPs Sunday afternoon into Monday morning/early afternoon in the the high chance range for snowfall. There is strong support in the ECMWF and GFS AI with slightly differences in the intensity of the coastal low and the track north and east. The latest NBM guidance is indicating 24-hr probabilities >4" of snowfall from the Capital Region south and east in the 30-40% range for the period ending 12Z/Mon. The 6" probabilities are in the 25-35% range for the same time frame ending 12Z/Mon from the Tri Cities south and east. There could be impacts on the Monday morning commute and we will continue to monitor the evolution and track of this storm over the next several days.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through 00z Thursday...Flying conditions as of 6:45 PM EST range from VFR at GFL/POU to MVFR at ALB/PSF. Mix of VFR/MVFR conditions should continue through the first few hours of the TAF period, but will then see a trend down to mainly MVFR cigs and vsbys, with pockets of IFR conditions after around 06z. Best chance for IFR is at POU/PSF closer to a stalled cold frontal boundary, but IFR cigs/vsbys due to low-level moisture also possible at ALB/GFL, especially if any breaks in the MVFR stratus deck develop. Low confidence on how widespread IFR or lower cigs and vsbys will be tonight, however.

Some slight improvement expected tomorrow for a brief period around mid-morning, but then precipitation develops along the stalled frontal boundary. Latest forecast trends have delayed start time of precipitation slightly, and have used prob30 groups to try to time out the onset of precip. This may need to be refined/adjusted later with future TAFs. Once precip begins, it will be mostly snow at GFL, any rain/snow mix will change to snow at ALB/PSF, and POU will see mainly rain with some sleet or freezing rain potentially mixing in tomorrow evening. Mainly MVFR cigs and IFR vsbys expected once precip begins.

Winds will generally be at 5 kt or less through tonight, increasing to 4-8 kt from the N/NE tomorrow morning, continuing through the end of the TAF period.

Outlook...

Wednesday Night: High Operational Impact. Definite SN. Thursday: No Operational Impact. NO SIG WX. Thursday Night: Low Operational Impact. Slight Chance of SN. Friday: High Operational Impact. Definite RA...SN. Friday Night: High Operational Impact. Likely RA...SN. Saturday: Moderate Operational Impact. Chance of RA. Saturday Night: Low Operational Impact. Slight Chance of SHSN. Sunday: Moderate Operational Impact. Chance of SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Weather Advisory from noon Wednesday to 4 AM EST Thursday for NYZ032-033-038>041-047>054-058>061-063- 082>084. MA...Winter Weather Advisory from noon Wednesday to 4 AM EST Thursday for MAZ001-025. VT...Winter Weather Advisory from noon Wednesday to 4 AM EST Thursday for VTZ013>015.